The present invention relates to toner and developer compositions, and more specifically, to negatively charged toner compositions comprised of certain charge enhancing additives. The toners and developers of the present invention can be selected for a number of electrophotographic imaging and printing processes including known xerographic processes. Also, the toners and developers of the present invention can be utilized for color, inclusive of trilevel color xerography, reference U.S. Pat. Nos. 4,948,686; 5,212,036; 5,208,129, and full process color, reference U.S. Pat. No. 5,275,905, the disclosures of which are totally incorporated herein by reference. In embodiments, there are provided in accordance with the present invention toner compositions comprised of a polymer or polymer resins, pigment particles or dye molecules, and aluminum salt mixtures of charge enhancing additives obtained, for example, by the reaction of an inorganic aluminum salt, such as aluminum halide like chloride or aluminum sulfate, with a mixture of alkylsalicylic acid and an alkoxy benzoic acid. In embodiments, the present invention is directed to toners with mixtures of aluminum salts of di-tertiary-alkyl, especially butylsalicylic acid and nonyloxybenzoic acid charge enhancing additives. Toners with the forementioned charge additives in embodiments of the present invention enable the provision of developers with substantially stable negative triboelectical toner characteristics which permit the generation of high quality images subsequent to development, that is images with substantially no background deposits and substantially no smearing for a broad range of relative humidity conditions, that is for example from between about 20 to 90 percent relative humidity at an effective range of, for example, temperature zones ranging, for example, from between about 20.degree. C. to about 80.degree. C. Also, the toners of the present invention possess a strongly negative charge, and wherein in embodiments the charge additive mixture may also function as a lubricant. Other advantages of the present invention include enabling negatively charged toners containing positive charging pigments and overcoming or minimizing the charging generated by surface additives.
Toners with certain aluminum charge enhancing additives are known, reference U.S. Pat. No. 4,845,003, the disclosure of which is totally incorporated herein by reference. The charge additives of the aforementioned patent comprise an aluminum compound of a hydroxycarboxylic acid which may be substituted with alkyl and/or aralkyl, reference the Abstract for example. Infrared analysis of a number of the aluminum charge enhancing additives of the '003 patent indicates the presence of free 3,5-di-t-butylsalicylic acid in significant amounts. The toner/developer performance properties and characteristics of the present invention are superior in some respects as compared, for example, to the toners of the '003 patent. For example, toners with the charge enhancing additive mixture of the present invention possess substantially lower CWS and CLC than toners of the '003 patent; CWS=Corrected Wrong Sign toner and CLC=Corrected Low Charge as determined by Charge Spectra analyses. The aforementioned lower characteristics with the toners of the present invention in embodiments enable, for example, developed images of excellent color, excellent image resolution with substantially no background deposits, and substantially stable triboelectric characteristics.
Toners with charge enhancing additives including additives that assist in providing a negative charge to the toner, such as orthohalocarboxylic acids, certain metal complexes and the like, are known. Also known are positively charged toners, reference for example U.S. Pat. Nos. 4,298,672; 4,338,390 and 4,560,635, the disclosures of which are totally incorporated herein by reference.
The following U.S. Pat. Nos. are also mentioned: 4,656,112, which discloses, for example, toners with a zinc complex compound of an aromatic hydroxycarboxylic acid with or without a substituent as a charge agent, see the Abstract, and column 2; and as background interest 4,411,974.
Processes for obtaining electrophotographic, including xerographic, and two-colored images are known. In U.S. Pat. No. 4,264,185, the disclosure of which is totally incorporated herein by reference, there is illustrated an apparatus for forming two-color images by forming a bipolar electrostatic image of a two-color original document on a photoconductive drum. A first developing unit applies a toner of a first color and polarity to the drum and a second developing unit applies a toner of a second color and polarity to the drum to form a two-color electrostatic image which is transferred and fixed to a copy sheet. A bias voltage of the first polarity is applied to the second developing unit to repel the toner of the first color and prevent degradation of the first color toner image. A bias voltage of the second polarity is applied to the first developing unit to prevent contamination of the first color toner with the second color toner.
In U.S. Pat. No. 4,308,821, there is disclosed a method and apparatus for forming two-color images which employs two magnetic brushes. The first developed image is not disturbed during development of the second image since the second magnetic brush contacts the surface of the imaging member more lightly than the first magnetic brush, and the toner scraping force of the second magnetic brush is reduced in comparison with that of the first magnetic brush by setting the magnetic flux density on a second nonmagnetic sleeve with an internally disposed magnet smaller than the magnetic flux density on a first magnetic sleeve, or by adjusting the distance between the second nonmagnetic sleeve and the surface of the imaging member. In addition, the toners selected may have different quantities of electric charge.
Further, U.S. Pat. No. 4,378,415, the disclosure of which is totally incorporated herein by reference, illustrates a method of highlight color imaging which comprises providing a layered organic photoreceptor having a red sensitive layer and a short wavelength sensitive layer, subjecting the imaging member to negative charges, followed by subjecting the imaging member to positive charges, imagewise exposing the member, and developing with a colored developer composition comprising positively charged toner components, negatively charged toner components and carrier particles. In U.S. Pat. No. 4,430,402, there is illustrated a two-component type dry developer for use in dichromatic electrophotography which comprises two kinds of developers, each of which are comprised of a toner and a carrier. Dichromatic images are formed by developing a both positively and negatively electrified electrostatic latent image successively with toners different in polarity and color from each other, wherein one carrier becomes positively charged by friction with either of the two toners while the other carrier becomes negatively charged by friction with either of the two toners.
Furthermore, in U.S. Pat. No. 4,525,447, the disclosure of which is totally incorporated herein by reference, there is illustrated an image forming method which comprises forming on a photosensitive member an electrostatic latent image having at least three different levels of potentials, or comprising first and second latent images and developing the first and second latent images with a three component developer.
Toners with certain zinc or aluminum salicylate complex charge enhancing additive in admixture with a second nonmetal containing charge enhancing additive are illustrated in copending application U.S. Ser. No. 755,979, the disclosure of which is totally incorporated herein by reference. The toner compositions of the aforementioned patent application contain, for example, a blend of two known CCA's, one positive and the other negative. With the present invention, the synthesized mixture contains a complete novel charge director mixture of a zinc 3,5-di-tert-butyl salicylate compound and an alkyl pyridinium halide compound as the charge control additive mixture, a resin, a colorant, a colloidal silica external additive, and a metal salt of a fatty acid external additive.
In U.S. Pat. No. 5,250,381, the disclosure of which is totally incorporated herein by reference, there is illustrated a negatively charged toenr composition comprised of resin particles, pigment particles, and an aluminum charge enhancing additive obtained from the reaction of an aluminum inorganic salt solution, and coumarin-3-carboxylic acid
In copending application U.S. Ser. No. 973,509, the disclosure of which is totally incorporated herein by reference, there is illustrated a toner composition comprised of resin, pigment and a charge enhancing additive of the formulas ##STR2## wherein R.sub.1 is selected from the group consisting of hydrogen and alkyl, and n is zero, 1, 2, 3 or 4.